At present, licensed frequency band resources are limited. To further increase a capacity, an operator may provide a data service for user equipment by using an unlicensed frequency band. Wireless Fidelity (Wi-Fi) is a main technology used on an unlicensed frequency band, but a wireless local network (WLAN) access point (AP) using the Wi-Fi technology has disadvantages with regard to mobility, security, quality of service (QoS), and multiuser scheduling processing. Applying a Long Term Evolution (LTE) technology to an unlicensed frequency band can not only effectively utilize an unlicensed frequency band resource, but also provide more favorable wireless access, thereby satisfying increasing mobile broadband service requirements.
In an LTE system, data sending or receiving on an unlicensed frequency band resource may be implemented by using a licensed-assisted access Licensed-Assisted Access Using LTE (LAA-LTE) system based on carrier aggregation (CA). Currently, an unlicensed frequency band considered to be used in LAA-LTE is an unlicensed frequency band of 5 GHz granted by state governments. A listen before talk (LBT) rule needs to be used when a wireless communications system occupies the unlicensed frequency band for communication. Usually, before transmitting data by using the unlicensed frequency band, a communications device (including a network device such as a base station and/or a terminal device) needs to first perform listening. Therefore, data sending or receiving performed by the communications device on the unlicensed frequency band resource is occasional.
When operating on the unlicensed frequency band, a network device first needs to perform clear channel assessment. When the clear channel assessment succeeds, the network device obtains a time resource segment on the unlicensed frequency band, and starts to transmit data according to a specific resource configuration manner (for example, according to a preconfigured frame structure). However, a transmission channel reserved for uplink information is set at intervals on the unlicensed frequency band. When a time range reserved for the uplink information overlaps with a time range in which the network device sends downlink user data, transmission of the downlink user data is interrupted, to reserve the unlicensed frequency band resource for uplink information transmission. As a result, transmission of the downlink user data of the network device fails, and efficiency of transmitting data on the unlicensed frequency band is decreased.
Therefore, a communications technology on an unlicensed frequency band needs to be provided, to improve efficiency of transmitting data on the unlicensed frequency band resource.